Re: [OpenBIOS] [PATCH 1/4] Disable strict aliasing for all targets

[Laurent Vivier]

> Makefile.target |    1 +
> 1 files changed, 1 insertions(+), 0 deletions(-)
>
> diff --git a/Makefile.target b/Makefile.target
> index f94f450..bf83b5b 100644
> --- a/Makefile.target
> +++ b/Makefile.target
> @@ -25,6 +25,7 @@ STRIP  := $(TARGET)strip
> RANLIB := $(TARGET)ranlib
>
> CFLAGS+= -Os -g -DNATIVE_BITWIDTH_EQUALS_HOST_BITWIDTH -USWAP_ENDIANNESS
> +CFLAGS+= -fno-strict-aliasing

...

Why is this needed ?

Laurent

[PATCH 1/4] Disable strict aliasing for all targets

[Pavel Roskin]

On Tue, 2009-08-11 at 12:39 +0200, Laurent Vivier wrote:
> > +CFLAGS+= -fno-strict-aliasing
>
> ...
>
> Why is this needed ?

I suggested disabling strict aliasing for the filesystem sources back in
April:
http://lists.openbios.org/pipermail/openbios/2009-May/003691.html

At that time, I hoped to fix other warnings individually.  But I got a
reply suggesting that all strict aliasing should be disabled:

http://lists.openbios.org/pipermail/openbios/2009-May/003694.html

We still have some warnings about strict aliasing on PowerPC:

../drivers/fw_cfg.c:41: error: dereferencing type-punned pointer will
break strict-aliasing rules
../drivers/fw_cfg.c:51: error: dereferencing type-punned pointer will
break strict-aliasing rules

Most strict aliasing warnings can be resolved, but it's time consuming.
Considering the attitude to this issue, I decided that the best solution
would be to disable strict aliasing globally.

I'm using gcc 4.4.1 on PowerPC, so I'm probably seeing more warnings
than others.